A comparative study of different low-z liner materials in an ablation-dominated electrothermal mass accelerator for fusion fueling

A low-z ablation-dominated capillary with an ablation-free extension barrel is a concept that provides a plasma flow sufficient to propel fuel pellets into the tokamak fusion plasma chamber. The acceleration barrel is made from a non-ablating material to eliminate mixing the propelling plasma with any impurities evolving from the barrel ablation. A capillary discharge computer code, ETFLOW, has been developed to model plasma flow and acceleration of pellets for fusion fueling in magnetic confinement fusion reactors. The code incorporates a set of governing equations for both the capillary and the acceleration tube and ideal and non-ideal conductivity models. The joule heating in the energy conservation equation is only valid in the capillary section. The pellet momentum and kinetic energy are included in the governing equations of the barrel, with the addition of the effect of viscous drag terms. The capillary generates the plasma from the ablation of low-z liner materials "sleeves" inside the capillary. The acceleration of the pellet starts in the extension tube when the pressure of the plasma flow from the capillary reaches the release limit. The code results show exit velocities in excess of 2km/s for source/barrel systems with low-Z liner materials in the source and loaded with 5, 20, 45, and 80 mg pellets. An increase in the length of both the source and the acceleration barrel increases the pellet exit velocity with the limitation of slowdown effects for plasma expansion and cooling off inside the barrel.